Opium was known and frequently used in Roman society. Medical practice recognized its usefulness as an analgesic, soporific, anti-tussic or anti-diarrheic agent, as well as other currently unsupported uses with quasi-magical properties. It was additionally used as an ingredient in antidotes, panaceas and poisons. The authors present a non-exhaustive compilation of opium use according to medical doctors, writers and encyclopaedists of the time. Mythological and literary representations of the opium poppy reflected its diverse roles, being associated with prosperity and fertility, sleep, death and the underworld and with the art of medicine. Despite its free and routine use, there is no solid evidence of addiction, except the putative case of emperor Marcus Aurelius, consistently reported as one of the most likely cases of addiction to opium.